Prognosis and cardiac reserve are both important variables considered in the treatment of heart failure (HF) patients. Cardiac Power Output (CPO) can be determined using echocardiography and arterial blood pressure measurements. The purpose of this study is to assess the relationship between CPO and autonomic tone in heart failure patients during exercise. The goal is to predict CPO from heart rate variability (HRV) and blood pressure variability (BPV) assessment of parasympathetic activity. Other dependent variables will also be collected and used in the prediction models.